V.42 permits receivers to request the retransmission of lost data packets, although it does not provide a guarantee about how much time it will take to deliver the error-free data to the receiving side. V.42 is generally included in dial-up modems and even includes an high-level data link control-based protocol referred to as Link Access Procedure for Modems.

The V.42 protocol includes some well-defined characteristics:

• A non-error-correcting mode with V-series DCE, including asynchronous-to-synchronous conversion according to ITU Telecommunications Standardization Sector recommendations
• Permits error detection using a cyclic redundancy check. Error correction is performed using the automatic retransmission of data.
• Enables synchronous transmission through start-stop data conversion and an initial handshake in start-stop format that minimize DTE disruption